Ventricular cuff

ABSTRACT

In one general aspect, an implant includes a cuff defining an opening configured to receive a cannula coupled to a heart pump. The implant includes a coupling mechanism having a first position and a second position, the cuff being uncoupled from the cannula in the first position and the coupling mechanism coupling the cuff to the cannula in the second position. The implant includes a locking mechanism configured to secure the coupling mechanism in the second position, and the locking mechanism is configured to be moved to a locked position after the coupling mechanism is in the second position.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.14/817,819, filed Aug. 4, 2015, which application is a divisional ofU.S. application Ser. No. 13/410,670, filed Mar. 2, 2012, now issuedU.S. Pat. No. 9,144,637, issued Sep. 29, 2015, which application claimsthe full benefit of U.S. Provisional Patent Application No. 61/448,434,filed Mar. 2, 2011, and titled “VENTRICULAR CUFF,” all of which areincorporated herein by reference in their entirety.

TECHNICAL FIELD

This disclosure relates to ventricular cuffs.

BACKGROUND

Heart assist devices or pumps can be inserted in the circulatory systemto pump blood from either ventricle or atrium of a heart to thevasculature. A pump supplementing a ventricle is known as a ventricularassist device, or VAD. A VAD is useful when the ventricle alone isincapable of providing adequate blood flow.

BRIEF SUMMARY

In a general aspect, a cuff for attachment to a heart defines an openingto admit a cannula of a heart pump. A coupling mechanism couples thecuff about the cannula, and a locking mechanism secures the position ofthe cuff set by the coupling mechanism.

In another general aspect, an implantable system includes a cuff, asurface defining channels, and a clip having arms that extend into thechannels. The arms travel along the channels during movement of the clipbetween an unlocked position of the clip and a locked position of theclip. The clip permits the cuff to be coupled about a cannula when theclip is in the unlocked position, and the clip is configured to securethe cuff relative to the cannula when the clip is in the lockedposition.

Implementations can include one or more of the following features. Forexample, the implantable system includes a cover, and the clip iscaptured between the cover and the surface. The cannula has alongitudinal axis, and the clip moves between the unlocked position andthe locked position in a plane perpendicular to the longitudinal axis.The cover and the surface define a slot, and the clip travels along alinear direction through the slot to enter the locked position. Thechannels define detents, and when the cuff is not coupled to thecannula, movement of the clip from the unlocked position toward thelocked position engages the arms into the detents to impede the clipfrom entering the locked position. Each of the arms can engage a detentindependent of whether another arm engages a detent, and engagement ofany of the arms with a detent impedes the clip from entering the lockedposition. When the clip moves toward the locked position and the cuff iscoupled about the cannula, the arms engage the cuff to avoid thedetents. The arms include teeth configured to limit rotation of the cuffabout the cannula when the clip is in the locked position. A sealingring is disposed about the cannula, and the sealing ring is engageableto an inner surface of the cuff to couple the cuff to the cannula. Theclip includes a visual indicator disposed such that the visual indicatoris exposed when the clip is not in the locked position and the visualindicator is obscured when the clip is in the locked position. The clipincludes a latch that impedes the clip from exiting the locked position.

In another general aspect, an implant includes a cuff defining anopening configured to receive a cannula coupled to a heart pump and acoupling mechanism having a first position and a second position. Thecuff is uncoupled from the cannula in the first position and thecoupling mechanism couples the cuff to the cannula in the secondposition. The implant includes a locking mechanism configured to securethe coupling mechanism in the second position, and the locking mechanismis configured to be moved to a locked position after the couplingmechanism is in the second position.

Implementations can include one or more of the following features. Forexample, a first action positions the coupling mechanism in the secondposition, and a second action activates the locking mechanism to securethe coupling mechanism in the second position, and the second actionoccurs subsequent to and separate from the first action. The cannulaincludes a flange and a circumferential ridge, and the couplingmechanism is configured to capture the cuff about the cannula betweenthe flange and the circumferential ridge. The cannula includes (i) anattachment portion between the flange and the circumferential ridge and(ii) an inflow portion, and the attachment portion has an outer diametergreater than an outer diameter of the inflow portion. The cuff includesan inner portion, an outer portion, and a member each disposedconcentrically about the opening, the member being disposed between theinner portion and the outer portion, and the outer portion extending ina direction generally perpendicular to the member. The couplingmechanism includes a clamp coupled to the cuff and disposed about theopening.

Implementations can include one or more of the following features. Theclamp has a first end and a second end, the clamp configured such thatbringing the first end near the second end opens the clamp and movingthe two ends apart closes the clamp. The locking mechanism includes acam that defines a channel, the cam being coupled to the first end ofthe clamp and being configured to rotate about the first end, the secondend of the clamp being disposed in the channel and being configured totravel within the channel. The channel includes a curved portion, thecurved portion being configured to limit the motion of the second end ofthe clamp in the channel when the clamp is closed. The couplingmechanism includes an attachment member coupled about the opening of thecuff, the attachment member having one or more flanged portions thatextend outward from the opening, and the locking mechanism includes aclip configured engage the flanged portions to limit movement of thecuff relative to the cannula. The clip is configured to enter a slot inthe pump to secure the cuff to the pump. The attachment member includesone or more extensions each including a contact portion that extendstoward the opening, the cannula includes a tapered circumferentialridge, and the second position of the coupling mechanism, the contactportions are disposed between the pump and the circumferential ridgealong the length of the cannula.

In another general aspect, a cuff for attachment to a heart includes amember defining an opening, a seal coupled to the member and disposedabout the opening, and a clamp coupled to the seal and disposed aboutthe opening. The clamp has a first end and a second end, and the clampis configured such that (i) bringing the first end near the second endopens the clamp and (ii) moving the first end and the second end apartcloses the clamp.

Implementations can include one or more of the following features. Forexample, a cam defining a channel, the cam being coupled to the firstend of the clamp and being configured to rotate about the first end, thesecond end of the clamp being disposed in the channel and beingconfigured to travel within the channel.

In another general aspect, a cuff for attachment to a heart includes amember defining an opening, a linking member coupled to the member anddisposed about the opening, and an attachment member coupled to thelinking member and disposed about the opening. The linking memberextends about an outer surface of the attachment member. The attachmentmember is configured to attach the cuff to a cannula disposed throughthe opening. The attachment member has at least one flanged portionextending outward from the opening in a plane generally perpendicular toa circular portion of the attachment member.

Implementations can include one or more of the following features. Forexample, the linking member is molded over a portion of the attachmentmember, and the attachment member is coupled to the member through thelinking member. The attachment member includes at least one extensiondisposed generally perpendicular to the member, the extension having atapered portion disposed on a surface of the extension facing toward theopening. The attachment member defines circumferential groove configuredto admit a sealing ring. The linking member includes an elastomer. Thelinking member is configured to form a seal.

In another general aspect, a method of attaching a ventricular assistdevice to a patient, includes: attaching a cuff to a heart, the cuffdefining an opening; removing tissue of the heart through the opening ofthe cuff; inserting a cannula through the opening of the cuff; engaginga coupling mechanism to set a position of the cuff relative to thecannula; and engaging a locking mechanism to secure the position of thecuff relative to the cannula.

Implementations can include one or more of the following features. Forexample, selecting a location near the apex of the heart to attach thecuff. Engaging a cardiac bypass system so that blood is not circulatingthrough the heart. Engaging the coupling mechanism includes inserting atapered portion of the cannula into the cuff so that one or moreextensions of the cuff engage a groove defined adjacent to the taperedportion. Engaging the locking mechanism includes inserting a clip thatengages the cuff and a pump coupled to the cannula. Engaging thecoupling mechanism includes closing a clamp coupled to the cuff so thatthe clamp engages a groove defined in the cannula. Engaging the lockingmechanism includes capturing an end of a clamp to secure the clamp in alocked position. Engaging the coupling mechanism to set a position ofthe cuff relative to the cannula includes positioning the cuff such thatan inner surface of the cuff engages a sealing ring disposed about thecannula and a bottom surface of the cuff engages a surface of thecannula or a surface of a pump that is coupled to the cannula. Engagingthe locking mechanism includes moving a clip in a plane perpendicular tothe cannula. Engaging the locking mechanism includes moving a clip intoa locked position about the cuff, the clip limiting travel of thecannula out of the cuff. Engaging the locking mechanism includesengaging a latch that secures the clip in the locked position.

In another general aspect, a system includes a cuff having an annularmember defining an opening and an attachment member disposed about theopening. The attachment member includes a flanged portion orientedgenerally parallel to the annular member, and the flanged portionextends outward from the opening. A clip is configured to be coupledabout the attachment member between the annular member and the flangedportion.

Implementations can include one or more of the following features. Forexample, the system includes a pump assembly that includes a cannula,and the clip is configured to travel relative to the pump assembly froman unlocked position to a locked position in which the clip secures thecuff about the cannula. The clip is configured to travel along asubstantially linear path from the unlocked position to the lockedposition. When the cuff is coupled to the pump assembly and the clip isin the locked position, the clip impedes rotation of the cuff about thecannula. The cuff includes ridges disposed on the attachment member, andthe clip is configured to engage the ridges to impede rotation of thecuff. The clip is configured to engage the pump assembly such that thetravel of clip to the locked position is impeded when the cuff isimproperly seated about the cannula. The clip is configured to engagethe pump assembly such that travel of clip to the locked position isimpeded when the cuff is not coupled to the pump assembly. The systemincludes a visual indicator that is visible when the clip is not in thelocked position and is obscured when the clip is in the locked position.When the clip is in the locked position, engagement of the clip and thepump assembly impedes travel of the clip out of the locked position. Theclip has arms that are configured to extend about the cuff in the lockedposition, the arms being configured such that any of the arms can engagethe pump assembly to impede travel of the clip into the lockingposition.

In another general aspect, a system includes a cuff having a memberdefining an opening and an attachment member disposed about the opening.The attachment member includes (i) a clamp having a first end and asecond end, and (ii) a cam defining a channel. The cam is coupled to thefirst end of the clamp and is configured to rotate about the first end.The second end of the clamp is disposed in the channel and is configuredto travel within the channel.

The features described can be used in any appropriate combination andsubcombination, including combinations across multiple aspects describedabove. Features described with respect to one aspect can additionally oralternatively be included in implementations of any of the otheraspects. The details of one or more implementations are set forth in theaccompanying drawings and the description below. Other features,objects, and advantages will be apparent from the description anddrawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a pump installed at a heart.

FIG. 2A is a perspective view of a ventricular cuff.

FIG. 2B is a side view of a cannula for coupling to the ventricular cuff

FIG. 3 is an exploded view of the ventricular cuff.

FIG. 4A is a perspective view of a tube from which a seal member of theventricular cuff can be fabricated.

FIG. 4B is a perspective view of a seal member of the ventricular cuff.

FIG. 5A is a perspective view of a cam of the ventricular cuff.

FIGS. 5B to 5E are respectively top, bottom, lateral side, and oppositelateral side views of the ventricular cuff.

FIG. 6 is a side cross-sectional view of the ventricular cuff coupled tothe cannula across line 6-6 of FIG. 8D.

FIGS. 7A to 7D are top views illustrating the closing of a clamp of theventricular cuff.

FIGS. 8A to 8D and 9A to 9C are perspective views illustrating thecoupling of the ventricular cuff to the pump.

FIGS. 10A to 10D are perspective views illustrating a process forimplanting the ventricular cuff and the pump.

FIG. 11A is a perspective view of a ventricular cuff.

FIG. 11B is a side view of a cannula for coupling to the ventricularcuff of FIG. 11A.

FIG. 12A is a perspective view of an attachment member of theventricular cuff of FIG. 11A.

FIG. 12B is a side cutaway view of an extension of the attachmentmember.

FIG. 13A is a perspective view illustrating the top of a clip.

FIG. 13B is a perspective view illustrating the bottom of the clip.

FIG. 13C is a side view of a post of the clip.

FIGS. 14A to 14C are perspective views illustrating the engagement ofthe clip with a pump.

FIGS. 15A to 15C are perspective views illustrating the coupling of thepump of FIG. 14A to the ventricular cuff of FIG. 11A using the clip.

FIG. 16 is a side cross-sectional view of the ventricular cuff of FIG.11A coupled to the cannula of FIG. 11B across line 16-16 of FIG. 15C.

FIG. 17A is a perspective view of a ventricular cuff.

FIG. 17B is a side view of a cannula for coupling to the ventricularcuff of FIG. 17A.

FIG. 18A is a perspective view of an attachment member of theventricular cuff of FIG. 17A.

FIG. 18B is a cross-sectional view of a portion of the ventricular cuffof FIG. 17A.

FIGS. 19A and 19B are cross-sectional views illustrating the engagementof the ventricular cuff of FIG. 17A with the cannula of FIG. 17B.

FIG. 20 is a side cross-sectional view of the ventricular cuff of FIG.17A coupled to the cannula of FIG. 17B and secured to the pump of FIG.14A using the clip.

FIG. 21 is a perspective view of a pump, a cannula, and a ventricularcuff

FIG. 22A is a perspective view of the cuff of FIG. 21.

FIG. 22B is a side view of the ventricular cuff of FIG. 21.

FIG. 22C is a perspective view of an attachment member of theventricular cuff of FIG. 21.

FIG. 22D is a side cutaway view of the ventricular cuff of FIG. 21.

FIGS. 23A and 23B are side cutaway views of the cannula and ventricularcuff of FIG. 21.

FIGS. 24A and 24B are cross-sectional view of sealing rings.

FIG. 25A is a perspective view of the pump of FIG. 21.

FIG. 25B is an exploded view of the pump of FIG. 21.

FIG. 26A is a top perspective view of a clip that cooperates with thepump and the ventricular cuff of FIG. 21.

FIG. 26B is a bottom perspective view of the clip of FIG. 26A.

FIG. 26C is a side view of an end portion of an arm of the clip of FIG.26A.

FIG. 26D is a side cross-sectional view of a tooth of the clip of FIG.26A.

FIG. 27 is a perspective view of a surface of the pump of FIG. 21.

FIGS. 28A to 28C are perspective views illustrating different motions ofthe clip of FIG. 26A relative to the pump of FIG. 21.

FIGS. 29A to 29C are bottom views of different positions of the clip ofFIG. 26A relative to the pump of FIG. 21.

FIGS. 30A to 30C are top perspective views of different positions of theclip of FIG. 26A relative to the pump of FIG. 21.

FIG. 31 is a side cutaway view of the pump, the cannula, and theventricular cuff of FIG. 21.

DETAILED DESCRIPTION

Referring to FIG. 1, a ventricular assist system 10 for treating, forexample, a patient with a weakened left ventricle, includes a blood pump12 that receives blood from a patient's heart 14. The pump 12 is coupledto a cuff 20, which in turn is attached to the heart 14. The cuff 20 isattached to the heart by, for example, sutures that attach a portion ofthe cuff 20 to the apex of the left ventricle of the heart 14. The pump12 receives blood from the heart through an inflow cannula 50 (FIG. 2B)of the pump 12 disposed through an opening in the cuff 20.

Referring to FIGS. 2A and 2B, the cuff 20 defines an opening 30 thatadmits the inflow cannula 50. The cuff 20 includes a coupling mechanism,for example, a clamp 26 that couples the cuff 20 to the cannula 50. Thecuff 20 also includes a locking mechanism in the form of a cam 28 thatsecures the clamp 26 in a closed position. The locking mechanism, bymaintaining the position of the coupling mechanism, limits thepossibility of the cuff 20 accidentally becoming uncoupled from thecannula 50. The locking mechanism can secure the cuff 20 to the cannula50 such that, for example, removal of the cuff 20 from the cannula 50requires more than one action, or the cannula 50 is no longer free torotate or translate with respect to the cannula 50 without significantoutside influence, such as by a clinician.

Referring to FIG. 3, the cuff 20 is illustrated in a view illustratingindividual disassembled parts, including a fastening member 22, alinking member 24, the clamp 26, and the cam 28. The componentsillustrated can be preassembled and delivered to a clinician as a singleunit. The fastening member 22 is generally ring-shaped and includes acontact surface 23 to contact heart tissue. The fastening member 22 iscomposed of a material through which sutures can be placed, for examplea fabric such as polytetrafluoroethylene (PTFE) felt. In an implantedstate, sutures or staples bind the fastening member 22 to heart tissueto couple the cuff 20 to the heart 14. In one embodiment, the fasteningmember 22 and the linking member 24 are pre-assembled together as oneunit.

Referring to FIGS. 4A and 4B, the linking member 24 can be fabricated byreshaping a tube 25 formed of, for example, an elastomer such assilicone. The linking member 24 is formed, for example, by folding anupper portion 32 of the tube 25 and a lower portion 33 of the tube 25about an outer circumference 31 of the tube 25. The resulting linkingmember 24 defines a circumferential groove 34 between generally parallelring-shaped portions 35, 36. The linking member 24 also includes acircumferential inner surface 40 that forms a seal with the cannula 50.

The linking member 24 can also be fabricated to include ring-shapedreinforcement members 37, 38 (FIG. 6) that includes, for example, a meshmaterial or a knitted fabric formed of a material such as polyester. Aknitted fabric or mesh material is embedded into a silicone sheet. Thesilicone sheet is die-cut into ring-shaped portions 35, 36 thatrespectively include the ring-shaped reinforcement members 38, 37. Thering-shaped portions 35, 36 are then placed in a silicone mold andovermolded with additional silicone. The molded silicone binds thering-shaped portions 35, 36 together and creates a flexible connectionbetween the ring-shaped portions 35, 36, which include the reinforcementmembers 38, 37.

Referring to FIG. 2A and FIG. 3, the clamp 26 includes a circularportion 70 formed of a resilient material, such as metal wire. Forexample, the circular portion 70 can be formed of stainless steel or acobalt chromium alloy, each of which can provide implantability, longterm stability, and resiliency. In the assembled cuff 20, the circularportion 70 is disposed in the circumferential groove 34 of the linkingmember 24. The linking member 24 is thus couples the clamp 26 to thefastening member 22. Sutures 42 pass through the fastening member 22 andthe ring-shaped portions 35, 36 of the linking member 24, capturing thecircular portion 70 in the linking member 24 and coupling the linkingmember 24 to the fastening member 22. The reinforcement members 37, 38limit tearing of the linking member 24 by the sutures 42. In additionto, or instead of, sutures 42, the linking member 24 can be coupled tothe fastening member 22 by an adhesive or by overmolding the linkingmember 24 over a portion of the fastening member 22.

The clamp 26 has a relaxed position toward which it wants to returnafter a load is applied to open or close the clamp 26. The circularportion 70 is expanded by moving the arms 72, 74 closer together. Thecircular portion 70 is contracted by increasing the distance between thearms 72, 74. Expansion of the circular portion 70 beyond the relaxedposition loads the circular portion 70, causing the circular portion 70to exert a force that tends to contract the circular portion 70 (e.g.,an inward radial force). Conversely, compression of the circular portion70 beyond the relaxed position loads the circular portion 70 such thatthe circular portion 70 exerts a force to expand the circular portion 70(e.g., an outward radial force).

The clamp 26 includes a pivot arm 72 and a travelling arm 74 that extendfrom the circular portion 70. The pivot arm 72 and the travelling arm 74provide leverage to expand and contract the circular portion 70, thusopening and closing the clamp 26. The pivot arm 72 includes a pivot end73, and the travelling arm 74 includes a travelling end 75. The ends 73,75 extend generally perpendicular to their respective arms 72, 74. Theends 73, 75 each pass through the cam 28 and are captured in the cam 28by a cap 76, 77.

Referring to FIGS. 5A to 5E, the cam 28 includes a top side 78, a bottomside 79, and opposite lateral sides 80, 81. The cam 28 can be formed of,for example, polyether ether ketone

(PEEK) or stainless steel. The cam 28 defines a pivot hole 82 thatadmits the pivot end 73, and defines a channel 83 that admits thetravelling end 75. About the pivot hole 82, in the top side 78, the cam28 defines a recess 84 that receives the cap 76. Opposite the recess 84,the cam 28 includes a boss 89 that extends from the bottom side 79. Theheight, H, of the boss 89 maintains a space between the pivot arm 72 andthe bottom side 79. By contrast, the travelling arm 74 can contact thebottom side 79. The two arms 72, 74 travel in different planes separatedby the distance H. Because the boss 89 maintains the pivot arm 72 at adistance from the bottom side 79, the travelling arm 74 can moverelative to the pivot arm 72 without contacting the pivot arm 72. Thecap 77 is disposed adjacent to the top side 78 and the cap 76 isdisposed in the recess 84 such that the caps 76, 77 do not contact eachother during operation of the clamp 26.

The channel 83 defines a path, such as a curve, between a detent 85 andan end 86 located near the pivot hole 82. The detent 85 includes ahooked portion of the channel 83 that captures the travelling end 75 tosecure the clamp 26 in the closed position.

The cam 28 includes an extension 87 that indicates proper placement ofthe cuff 20 relative to the pump 12. As the cuff 20 becomes coupled tothe cannula 50, the extension 87 engages the surface 13 of the pump 12to indicate proper placement of the cuff 20 relative to the pump 12. Inaddition, the extension 87 aligns the cam 28 in a plane generallyparallel to the surface 13. Alignment of the cam 28 with respect to thesurface 13 reduces the likelihood that the cam 28 may engage a portionof the pump 12 and improperly impede the clamp 26 from closingcompletely. The cam 28 also includes a raised portion 88 extending fromthe top side 78, which facilitates manipulation of the cam 28. Theraised portion 88 is rounded to rest against the outer circumference ofthe pump 12 when the cam 28 is locked (see FIG. 9C). The raised portion88 defines a slot 90 in which a tool or surgical instrument can beinserted to unlock the cam 28. The slot 90 can be used to pry open theclamp 26, for example, if tissue in-growth makes manual manipulation ofthe cam 28 difficult.

Manipulation of the cam 28 moves the clamp 26 between open and closedpositions. In the open position, the clamp 26 permits a proximal portion52 of the cannula 50 to pass through the opening 30. In the closedposition, the clamp 26 presses inward to couple the cuff 20 to thecannula 50. In the closed position, the clamp 26 presses the linkingmember 24 into engagement with the cannula 50, and the circumferentialinner surface 40 of the linking member 24 forms a seal with the cannula50.

Referring to FIG. 2B, the cannula 50 is shown by itself here but isgenerally an integrated component of the pump 12. In someimplementations, the pump 12 can receive different interchangeablecannulas to achieve an appropriate fit in a particular anatomy. Thecannula 50 includes the proximal portion 52 that passes through theopening 30 into the heart 14 and a distal portion 54 housed within thepump 12. Along the length of the cannula 50, between the proximalportion 52 and the distal portion 54, the cannula 50 includes acircumferential tapered portion 56, a circumferential ridge 58, and acircumferential flange 62. The cannula 50 defines a circumferentialgroove 60 in which the clamp 26 and the linking member 24 are received.

To couple the cannula 50 to the cuff 20, the proximal portion 52 ispassed through the opening 30, such that the circumferential taperedportion 56 engages the circumferential inner surface 40 of the linkingmember 24, guiding the cannula 50 into alignment with the cuff 20.Further advancement of the cannula 50 causes the circumferential ridge58 to travel past the circular portion 70 of the clamp 26. The action ofthe circumferential ridge 58 passing the circular portion 70 provides aclinician tactile feedback about the proper location of the components.The circumferential flange 62 limits further travel of the cannula 50relative to the cuff 20, positioning the circular portion 70 of theclamp 26 about the circumferential groove 60. The fastening member 22 isdisposed about the cannula 50, generally about the circumferential ridge58.

The cuff 20 is sized so that the inner diameter of the cuff 20 isgreater than the outer diameter of the proximal portion 52, whichfacilitates insertion of the proximal portion 52. With the clamp 26 inits open position, the size of the inner diameter of the cuff 20approximates that of the outer diameter of the circumferential ridge 58.The circumferential ridge 58 is rounded, permitting the linking member24 to slide over the circumferential ridge 58 and into thecircumferential groove 60. Thus a clinician can determine that the cuff20 is properly positioned relative to the cannula 50 by experiencing thetactile sensation of the linking member 24 entering the circumferentialgroove 60.

Referring to FIG. 6, the cuff 20 is coupled to the cannula 50 by movingthe clamp 26 to its closed position. In the closed position, the innerdiameter of the clamp 26 is smaller than the outer diameter of thecircumferential ridge 58. The clamp 26 presses the linking member 24into the circumferential groove 60, forming a seal and capturing thecannula 50 in the cuff 20. The outer diameter of the cannula 50 at thecircumferential groove 60 is larger than the outer diameter of theproximal portion 52. The differential in diameter allows passage of acoring tool through the cuff 20. In some instances, the coring tool canbe slightly larger than the proximal portion 52 of the cannula 50. Inaddition, the differential in diameter can allow the clinician tofurther confirm proper placement of the cuff 20 relative to the cannula50. A clinician can confirm proper placement by applying a small axialload that would tend to separate the cannula 50 from the cuff 20. If thecannula 50 and the cuff 20 separate easily, then the cuff 20 isimproperly seated. If cannula 50 and the cuff 20 remain coupled,however, the cuff 20 is properly seated.

Referring to FIG. 7A, as the clamp 26 moves from the open position ofFIG. 7A to the closed position of FIG. 7C, the cam 28 rotates about thepivot end 73 in a plane. As the cam 28 rotates, the travelling end 75travels through the channel 83. In the open position, the pivot arm 72and the travelling arm 74 are located near each other, and the circularportion 70 is expanded beyond its relaxed position. In this position,the clamp 26 can admit the circumferential ridge 58 of the cannula 50through the opening 30. The travelling end 75 is located at the end 86of the channel 83 nearest the pivot end 73.

Because the circular portion 70 is loaded, the circular portion 70exerts a force on the end 75 in the direction of arrow F₁ to separatethe pivot arm 72 and the travelling arm 74. Nevertheless, the openposition is stable because the force acts away from the length of thechannel 83 and instead presses the travelling end 75 into the end 86 ofthe channel 83. As a result, the open position can be maintained whilethe cannula 50 is placed relative to the clamp 26.

From the open position, a clinician closes the clamp 26 by exerting aforce on the side 80 of the cam 28, causing the cam 28 to rotate in aplane about the pivot end 73. A small rotation of the cam 28 in thedirection of arrow R₁ brings the length of the channel 83 into closeralignment with the direction of force, F₁, exerted by the circularportion 70 on the travelling end 75. The force exerted by the circularportion 70 continues the rotation of the cam 28 about the pivot end 73as the clamp 26 continues to close.

Referring to FIG. 7B, the clamp 26 is in an unstable position betweenthe open position and the closed position. Force exerted by the loadedcircular portion 70 continues to rotate the cam 28 in the plane andclose the clamp 26. The distance between the pivot arm 72 and thetravelling arm 74 increases, and the circular portion 70 contracts,resulting in an overlap of the circular portion 70 of a distance, D₁.The clinician is not required to apply additional force on the cam 28 tomove the clamp 26 to the closed position. The clamp 26 exerts a force inthe direction of arrow F₂, moving the end 75 through the channel 83. Asthe travelling end 75 proceeds through the channel 83, the cam 28continues to rotate about the pivot end 73, as indicated by arrow R₂.

Referring to FIG. 7C, with the clamp 26 in the closed position, thecannula 50 is captured within the clamp 26. The size of the circularportion 70 in the closed position can be selected to permit rotation ofthe cannula 50 relative to the cuff 20 or to limit such rotation.

The closed position is stable. The circular portion 70 is in itsunloaded, relaxed position. As a result, the clamp 26 does not exert aforce on the travelling end 75 in either direction along the channel 83.The travelling end 75 is located in the channel 83 near the detent 85but not in the detent 85.

To lock the clamp 26, the clinician applies a force to the side 80 ofthe cam 28, in the direction of arrow C, which rotates the cam 28further in the plane. As the cam 28 rotates, the cam 28 exerts a forceon the travelling end 75 that is generally aligned with the channel 83,causing the arms 72, 74 to separate further. Rotation of the cam 28moves the travelling end 75 into the detent 85 and loads the circularportion 70. This action closes the circular portion 70 beyond itsrelaxed position, reducing the diameter of the circular portion 70 tolock the clamp 26 about the circumferential groove 60 of the cannula 50.Locking the clamp 26 also causes the circular portion 70 to exert aninward radial force to compress the linking member 24 and press thecircumferential inner surface 40 into the circumferential groove 60,forming a hemostatic seal.

Referring to FIG. 7D, in the locked position of the clamp 26, the cam 28impedes the clamp 26 from opening. The circular portion 70 is slightlycompressed beyond its relaxed position, such that the overlap distanceD₃ is larger than D₂. The loaded circular portion 70 exerts a force onthe travelling end 75 in the direction of arrow F₃, which presses thetravelling end 75 into the detent 85. Because the circular portion 70forces the travelling end 75 into the detent 85, the travelling end 75is impeded from traveling through the channel 83 and moving the clamp 26into the open position.

To open the clamp 26 from the locked position, the travelling end 75must be dislodged from the detent 85. The clinician applies a force, forexample, in the direction of arrow U, to overcome the force of theloaded circular portion 70. The force rotates the cam 28 in the planesuch that the travelling end 75 slides out of the detent 85.

From the closed position (FIG. 7C), the clamp 26 can be opened byexerting a force on the side 81 away from the circular portion 70, whichrotates the cam 28 opposite the direction of arrows R₁ and R₂ until theopen position is reached. The cannula 50 can then be removed orrepositioned relative to the clamp 26 before the clamp 26 is closedagain.

Referring to FIG. 8A, the cuff 20 is in the open position before beingcoupled to the cannula 50 of the pump 12. Generally, during theimplantation process, the cuff 20 will first be attached to the heart 14and then heart tissue will be removed to admit the proximal portion 52of the cannula 50. In addition, or alternatively, heart tissue can alsobe removed before the cuff 20 is attached to the heart 14.

The cannula 50 is fixedly coupled to the pump 12, for example, thecannula 50 can be sealed and welded to the pump 12. Alternatively, thecannula 50 can be removably coupled to the pump 12, for example, by athreaded connection or by a mechanism that permits the cannula 50 tosnap into place. A clinician can select a cannula 50 that best fits theanatomy of the patient, and can couple the cannula 50 to the pump 12prior to or during a procedure. When the cannula 50 is coupled to thepump 12, the distal portion 54 is housed within the pump 12 and theproximal portion 52 extends from a top surface 13 of the pump 12. Aclinician may select a cannula 50 that extends an appropriate distanceinto the heart 14. For example, a clinician may a cannula 50 with afirst length for a left VAD so that the cannula 50 extends the properdistance into the heart 14. For implantation of a right VAD, however,the clinician may use a cannula with a different length so that thecannula extends a different distance into a heart.

To couple the cannula 50 to the cuff 20, the pump 12 and the cannula 50are advanced toward the cuff 20 so that the proximal portion 52 of thecannula 50 enters the opening 30. As the cannula 50 travels relative tothe cuff 20, the circumferential ridge 58 engages the circumferentialinner surface 40 of the linking member 24. Further travel of the cannula50 relative to the cuff 20 advances the circumferential ridge 58 throughthe linking member 24, so that the clamp 26 and the linking member 24are disposed about the circumferential groove 60.

Advancing the circumferential ridge 58 through the linking member 24produces tactile feedback for the clinician, such as a snap-likesensation. The tactile feedback indicates that the cuff 20 is properlyseated against the circumferential flange 62 and that the circularportion 70 is disposed about the circumferential groove 60. In someimplementations, as the circumferential ridge 58 engages the linkingmember 24 disposed over the circular portion 70, the circumferentialridge 58 slightly expands the circular portion 70. When thecircumferential ridge 58 passes through the clamp 26, the clamp 26contracts to its open position, contributing to the tactile feedbackexperienced by the clinician.

Referring to FIGS. 8B and 9A, the cuff 20 is disposed about the cannula50, with the linking member 24 partially disposed in the circumferentialgroove 60. In this position, the clamp 26 can be closed to capture thecannula 50 in the cuff 20. To close the clamp 26, the clinicianmanipulates the cam 28 to begin rotating the cam 28 about the pivot end73, in the direction of arrow R₃.

Referring to FIGS. 8C and 9B, the resilient force of the clamp 26 movesthe travelling end 75 through the channel 83 defined in the cam 28,continuing the rotation of the cam 28 about the pivot end 73, in thedirection of arrow C₁. The circular portion 70 of the clamp 26 contractsand presses the linking member 24 into the circumferential groove 60.The contraction of the circular portion 70 captures the cannula 50within the cuff 20 because the circumferential ridge 58 cannot passthrough the circular portion 70.

Referring to FIGS. 8D and 9C, the clamp 26 is in a closed position andthe cam 28 is in a locked position, maintaining the clamp 26 in theclosed position. The travelling end 75 of the clamp 26 is located in thedetent 85 defined in the cam 28. From this position, the clamp 26 isunlikely to be opened accidentally, because significant force isrequired to remove the travelling end 75 from the detent 85. The topside 78 of the cam 28 is disposed against the top surface 13 of the pump12, and the raised portion 88 of the cam 28 rests against the outercircumference of the pump 12.

Referring to FIG. 10A, implantation of pump 12 to the heart 14 caninclude selecting a location to attach the cuff 20. For example, theapex 15 of the left ventricle can be selected as an operation site.

Referring to FIG. 10B, the cuff 20 is placed in contact with the heart14 at the selected operation site. The cuff 20 is attached to the heart14, for example, with sutures. In some embodiments, a cardiac bypasssystem is activated so that blood does not circulate through the heart14. A core section of heart tissue is removed through the opening 30 ofthe cuff 20. Alternatively, in some embodiments, the cuff 20 can beattached to the heart 14 and a core section of heart tissue can beremoved in the absence of a cardiac bypass. As another alternative, insome implementations, the core section of heart tissue can be removedbefore attaching the cuff 20 to the heart 14.

Referring to FIG. 10C, heart tissue has been removed so that theproximal portion 52 can be admitted through the opening 30 of the cuff20. The clamp 26 of the cuff 20 is moved to its open position (notshown) and the proximal portion 52 of the cannula 50 is received throughthe opening 30.

Referring to FIG. 10D, the proximal portion 52 advances through theopening 30 until the circular portion 70 of the clamp 26 is disposedabout the circumferential groove 60. The clinician determines that thecircular portion 70 is located about the circumferential groove 60 basedon (i) snap-like tactile feedback of the circumferential ridge 58passing through the linking member 24 and (ii) engagement of the linkingmember 24 to the circumferential flange 62. The clinician couples thecuff 20 to the cannula 50 by rotating the cam 28 in a plane generallyparallel to the top surface 13 of the pump 12. Rotation of the cam 28moves the clamp 26 to its closed position, in which the cannula 50 iscaptured within the cuff 20. The clinician rotates the cam 28 further inthe plane to engage the locking mechanism of the cam 28, impeding theclamp 26 from leaving the closed position. By engaging the lockingmechanism of the cam 28, orientation of the cuff 20 to the cannula 50can be secured such that axial movement of the cannula 50 relative tothe cuff 20 and rotation of the cannula 50 relative to the cuff 20 areboth impeded.

The size of the cuff 20 can be selected such that, when the pump 12 iscoupled to the cuff 20, the distance between the heart 14 and the topsurface 13 of the pump 12 is small. For example, the total height of thecuff 20 may be, for example, between approximately 2 mm andapproximately 10 mm. Because the cam 28 can be moved to a lockedposition by planar movement, the locking mechanism does not requireclearance between the cuff 20 and the top surface 13.

In addition, the inflow cannula 50 can define two or morecircumferential grooves between two or more circumferential ridges.Multiple circumferential grooves can provide different locations alongthe length of the cannula 50 at which the cuff 20 can be coupled. Aclinician couple the cuff 20 at a particular circumferential groove toselect the distance that the cannula 50 will extend into the heart 14.

The thickness of the fastening member 22 can be selected to adjust thelength that the cannula 50 extends into the heart 14. The use of athicker fastening member 22 can result in the cannula 50 extending ashorter depth into the heart 14 than the use of a thinner fasteningmember 22. A clinician may select a cuff 20 that includes a fasteningmember 22 of an appropriate thickness to set the distance that thecannula 50 extends into the heart 14.

A clinician may also adjust the distance that the cannula 50 extendsinto the heart by adding one or more spacers, such as a ring-shapedfabric washer, between the cuff 20 and the heart 14. For example, aclinician may place a spacer between the surface of the heart 14 and thecontact surface 23 of the fastening member 22. Sutures can be placedthrough the fastening member 22 and through the spacer to attach thecuff 20 at an appropriate distance from the heart 14.

In some implementations, the length of the proximal portion 52 of thecannula 50 can be varied to achieve a desired length of extension of theproximal portion 52 into the heart 14. For example, several inflowcannulas having proximal portions of different lengths can befabricated. A clinician can select an inflow cannula that has a proximalportion corresponding to the desired length of extension into the heartof a particular patient, and can couple the selected inflow cannula to apump before or during a procedure.

As an alternative to the clamp 26, the cuff 20 may include a resilientmetal split ring. A break or gap in the split ring permits the diameterof the split ring to expand as it travels over the circumferentialgroove 58 of the cannula 50. Once the split ring is located about thecircumferential groove 60, the split ring contracts into thecircumferential groove 60 to couple the cuff 20 to the cannula 50. Thesplit ring may thus be operated without arms extending from the splitring and without a cam.

Referring to FIGS. 11A and 11B, an alternative cuff 120 and analternative cannula 150 can be used to couple a pump 250 (FIG. 14A) toheart tissue. A coupling mechanism, for example, an attachment member126, couples the cuff 120 to the cannula 150. A locking mechanism in theform of a clip 200 (FIG. 13A) impedes the cuff 120 from becominguncoupled from the cannula 150.

The cuff 120 defines an opening 130 that admits a proximal portion 152of the cannula 150. The cuff 120 includes an annular fastening member122, a linking member 124, and the attachment member 126. The fasteningmember 122 can be sutured to heart tissue, and can include, for example,a fabric such as PTFE felt.

The linking member 124 is formed of, for example, an elastomer such assilicone, and includes a reinforcement member 128 (FIG. 16) such as amesh ring. The linking member 124 is disposed about an outercircumference of the attachment member 126 and serves as a linkingmember to couple the attachment member 126 to the fastening member 122,as discussed further below. The linking member 124 is coupled to thefastening member 122 by, for example, sutures. The linking member 124can also be molded directly to the fastening member 122. The linkingmember 124 includes a bottom surface 125 configured to engage agenerally flat circumferential flange 162 of the cannula 150, forming aface seal with the circumferential flange 162.

The cannula 150 includes the proximal portion 152 that enters theopening 130 of the cuff 120 and a distal portion 154 that is housed inthe pump 250. The cannula 150 includes a first circumferential taper 156that engages extensions 136 of the attachment member 126 and deflectsthem away from the cannula 150 as the cannula 150 advances through theopening 130. The cannula 150 includes a second circumferential taper 158and defines a circumferential groove 160 between the secondcircumferential taper 158 and the circumferential flange 162.

Referring to FIGS. 12A and 12B, the attachment member 126 is formed of,for example, a rigid material such as metal. The attachment member 126includes a ring portion 132 having a wall 133 with cutouts 134 thatdefine flexible extensions 136. Each extension 136 includes a lowertapered portion 138 (FIG. 12B) disposed on a free end 139 of theextension 136, facing inward toward the opening 130. As the firstcircumferential taper 156 of the cannula 150 is inserted through theopening 130, the lower tapered portions 138 engage the firstcircumferential taper 156, causing the extensions 136 to flex outwardfrom the opening 130 and permit the first circumferential taper 156 topass through the opening 130. When the lower tapered portions 138 aredisposed in the circumferential groove 160, the lower tapered portions138 engage the second circumferential taper 158 of the cannula 150 toimpede the cannula 150 from easily exiting the cuff 120. Each lowertapered portion 138 includes upper tapered portion 140, and the width ofeach lower tapered portion 138, W, decreases along the length of eachlower tapered portion 138, between the upper tapered portion 140 and thefree end 139.

The extensions 136 can have equal sizes or can be selected to havediffering sizes. For example, asymmetrical lengths of the extensions 136can cause the extensions 136 to engage the circumferential tapers 156,158 sequentially rather than consecutively during travel of the cannula150 relative to the cuff 120, reducing the force required to couple thecannula 150 to the cuff 120 or to uncouple the cannula 150 from the cuff120.

The amount of force required to deflect the extensions is correlatedwith the angle of the taper of the circumferential tapers 156, 158 andthe tapered portions 138, 140. The steepness of the taper angles can beselected such that different amounts of force along the length of thecannula 150 are required to couple the cuff 120 to the cannula 150 canremove the cuff 120 from the cannula 150. The engagement of tapers witha steep angle result in a lower percentage of axial force beingtransmitted radially outward than the engagement of shallower tapers.Thus to allow the cuff 120 to be coupled to the cannula 150 with asmaller force than the force required to remove the cuff 120 from thecannula 150, the tapers of the lower tapered portions 138 and thecircumferential taper 156 are less steep than the tapers of the uppertapered portions 140 and the circumferential taper 158. Accordingly,more force is required to decouple the cuff 120 than to couple the cuff120 to the cannula 150. The amount of force required to couple the cuff120 to and decouple the cuff 120 from the cannula 150 can be adjusted bythe materials selected for the attachment member 126, the thickness ofthe extensions 136, the length and width of the extensions 136, and thegeometry of the cutouts 134.

The attachment member 126 includes flanged portions 146, disposedbetween the extensions 136 along the outer circumference of theattachment member 126, at the bottom 141 of the attachment member 126.The flanged portions 146 extend generally perpendicular to the wall 133.When the cuff 20 is coupled to the cannula 150, the flanged portions 146are disposed in a plane generally parallel to the circumferential flange162 of the cannula 150. When the cuff 20 is locked to the cannula 150,the flanged portions 146 are captured between the clip 200 and thecircumferential flange 162, impeding the cuff 120 from becominguncoupled from the cannula 150.

The flanged portions 146 define holes 148 through which material of thelinking member 124 is molded or adhesive is applied to form mechanicallocks that secure the linking member 124 to the attachment member 126.Material of the linking member 124 is also molded or adhesively bondedthrough the cutouts 134 and over the ring portion 132. For example,silicone can be molded over the attachment member 126 and can be moldedover a portion of the fastening member 122. The linking member 124 canalso be coupled to the attachment member 126 with adhesive or sutures.The linking member 124 covers the flanged portions 146, an outer surface142 of the wall 133, and a portion of an inner surface 144 of the wall133 (FIG. 16).

The flanged portions 146 and extensions 136 are disposed symmetricallyalong the circumference of the attachment member 126, permitting theextensions 136 to engage the circumferential tapers 156, 158 evenlyabout the cannula 150, and permitting the flanged portions 146 to evenlypress the bottom surface 125 of the linking member 124 into engagementwith the circumferential flange 162. The attachment member 126 caninclude more or fewer flanged portions 146 and extensions 136 than thoseillustrated.

To couple the cannula 150 to the cuff 120, a clinician inserts theproximal portion 152 of the cannula 150 through the opening 130. As thecannula 150 advances through the opening 130, the first circumferentialtaper 156 passes the upper tapered portion 140 of the lower taperedportions 138. The engagement of the lower tapered portions 138 with thefirst circumferential taper 156 (which resists advancement of thecannula 150 by deflecting the extensions 136) ends abruptly, permittingthe extensions 136 to straighten so that the lower tapered portions 138reside in the circumferential groove 160. The sudden decrease inresistance to advancement of the cannula 150 produces a tactilesnap-like sensation, indicating to the clinician that the cannula 150 iscoupled to the cuff 120. The upper tapered portion 140 of the lowertapered portions 138 engage the second circumferential taper 158,impeding the cannula 150 from separating from the cuff 120. The bottomsurface 125 of the linking member 124 engages the circumferential flange162, limiting further advancement of the cannula 150 relative to thecuff 120.

After the cannula 150 and cuff 120 are coupled, the cannula 150 can beseparated from the cuff 120 by a force sufficient to deflect theextensions 136. Engagement of the upper tapered portions 140 with thesecond circumferential taper 158 deflects the extensions 136, allowingthe cannula 150 to be removed from the cuff 120.

Referring to FIGS. 13A and 13B, the clip 200 is used to secure the cuff120 about the cannula 150. The clip 200 cooperates with features of thepump 250, described below, to limit travel of the cuff 120 relative tothe cannula 150. The clip 200 includes a top side 202, a bottom side204, and opposite lateral sides 206, 208. The clip 200 can be formed of,for example, a rigid plastic, such as PEEK, or metal, such as titanium.

The clip 200 includes guide rails 212 and arms 214, and defines a recessor opening 215 or opening. The guide rails 212 guide the clip 200through a linear motion as the clip 200 is received by the pump 250. Theopening 215 admits a tool or a finger of the clinician to facilitatedisengagement of the clip 200 from its locked position relative to thecuff 120. The arms 214 are curved and resilient, and define an opening220. As the clip 200 moves relative to the pump 250, the pump 250 forcesthe arms 214 laterally outward, expanding the opening 220 and allowingthe arms 214 to extend about the linking member 124 of the cuff 120. Inthe locked position of the clip 200, the pump 250 forces the arms 214laterally inward to engage the linking member 124 and to secure the cuff120 to the pump 250.

The arms 214 include teeth 216 that extend from inner walls 217 of thearms 214 toward the opening 220. In the locked position of the clip 200,the teeth 216 are disposed over the flanged portions 146 of theattachment member 126, thus capturing the flanged portions 146 betweenthe teeth 216 and the circumferential flange 162 of the cannula 150.Between the teeth 216 are gaps 218 that permit the arms 214 to flexlaterally as the clip 200 is received by the pump 250. When the clip 200is in a locked position about the cuff 120, the teeth 216 engage thelinking member 124 of the cuff 120 to impede rotation of the cuff 120relative to the clip 200 and the pump 250.

Each arm 214 includes a post 219 extending from the bottom side 204 thatis received in one of the channels 254 (FIG. 14A) defined by the pump250. As the pump 250 receives the clip 200, the posts 219 travel throughthe channels 254, directing the lateral flexion of the arms 214. Theposts 219 each include angled walls 221, 222 (FIG. 13C) that engageangled walls 257, 258 (FIG. 16) of the pump 250 that define the channels254, capturing the posts 219 in the channels 254.

Referring to FIG. 14A, the pump 250 is coupled to the cannula 150 andreceives a clip 200. The pump 250 defines generally parallel slots 252that receive the guide rails 212 of the clip 200. The pump 250, in a topside 256, also defines the channels 254 that receive the posts 219between the angled walls 257, 258 (FIG. 16). The angled walls 257, 258capture the posts 219, impeding the posts 219 from leaving the channels254 and maintaining the arms 214 in a plane above the top side 256. Theportion of the pump 250 that defines the channels 254 can be an integralcomponent of, for example, a motor housing of the pump, or can be aseparate component that attaches to the pump 250, for example, withwelds, screws, or other fastening mechanisms.

The pump 250 defines an entry recess 255 at each channel 254 that admitsthe post 219. The distance between the entry recesses 255 is larger thanthe distance between the posts 219 when the arms 214 of the clip 200 arenot flexed.

To insert the posts 219 into the channels 254, the clinician flexes thearms 214 outward, loading the resilient arms 214 and permitting theposts 219 to enter the channels 254 at the entry recesses 255. After theposts 219 are positioned in the entry recesses 255, the arms 214 flexinward to their natural resting condition, moving the posts 219 in thechannels 254 away from the entry recesses 255. Because the posts 219 arecaptured in the channels 254, the clip 200 will not separate from thepump 250 until the clinician flexes the arms 214 outward and upward,permitting the posts 219 to leave the channels 254 at the entry recesses255. The pump 250 can be provided with the clip 200 already positionedin the channels 254, and thus already captured by the pump 250, tostreamline the implantation procedure.

A first portion 260 of the channels 254 curves outward about the cannula150 to spread the arms 214, permitting the arms 214 to extend about thecannula 150 and the linking member 124 of the cuff 120. A second portion262 of the channels 254 curves inward toward the cannula 150, moving thearms 214 inward about the cannula 150.

Referring to FIG. 14B, the guide rails 212 of the clip 200 enter theslots 252, and the posts 219 are captured in the channels 254. The clip200 travels in a generally linear direction relative to the pump 250, inthe direction of arrow I₁, until the clip 200 reaches the position ofFIG. 14C. As the clip 200 is advanced into the pump 250, the force inthe direction of arrow I₁ causes the posts 219 to deflect outward in thechannels 254. Once the posts 219 have reached the peak distance betweenthe channels 254, the insertion force required in the direction of arrowlessens as the inward deflection force of the arms 214 drive the clip200 through the second portion 262 of the channels 254. The clip 200travels linearly as the posts 219 travel through the channels 254, untilthe position of FIG. 14C is reached in which the arms 214 are in theirrelaxed position.

To move the clip 200 back to the unlocked position, the clip 200 isretracted in a direction opposite the arrow I₁, and the posts 219 travelin the opposite direction through the channels 254. During removal ofthe clip 200, the second portion 262 expands the arms 214 and the firstportion 260 permits the arms 214 to become closer together. The angle ofthe first portion 260 is less steep than the angle of the second portion262, which results in the force to remove the clip 200 being higher thanthe force to move the clip 200 into the locking position.

Referring to FIG. 15A, a clinician moves the pump 250 and the cannula150 relative to the cuff 120, in the direction of arrow B, so that theproximal portion 152 enters the opening 130 of the cuff 120. As thecannula 150 advances, the first circumferential taper 156 deflects theextensions 136 away from the cannula 150. The first circumferentialtaper 156 and the second circumferential taper 158 advance past thetapered portions 138 of the extensions 136. As the first circumferentialtaper 156 advances past the tapered portions 138, the deflectedextensions 136 straighten, forcing the tapered portions 138 into thecircumferential groove 160. The clinician experiences tactile feedback,such as a snap-like sensation, that indicates that the cannula 150 iscoupled to the cuff 120. The bottom surface 125 of the linking member124 engages the circumferential flange 162 of the cannula 150. In someimplementations, the bottom surface 125 engages a surface of the pump250 as an alternative to, or in addition to, engaging a portion of thecannula 150.

Referring to FIG. 15B, the clinician advances the clip 200 into the pump250. The guide rails 212 of the clip 200 travel in the slots 252,guiding the clip 200 as it travels linearly in a plane above the topside 256, in the direction of arrow I₂. As the clip 200 travels relativeto the pump 250, the arms 214 flex laterally due to engagement of theposts 219 with the angled walls 257, 258 defining the channels 254. Thearms 214 move laterally outward to admit the linking member 124 and thenlaterally inward to engage the linking member 124.

Referring to FIG. 15C, the clip 200, in its locked position, limitstravel of the cuff 120 relative to the cannula 150. The engagement ofthe posts 219 with the angled walls 257, 258 that define the channels254 forces the arms 214 inward such that the teeth 216 of the arms 214are disposed over the flanged portions 146 of the attachment member 126.The flanged portions 146 are captured between the teeth 216 and thecircumferential flange 162. The engagement of the teeth 216 to thelinking member 124 presses the bottom surface 125 against thecircumferential flange 162, forming a seal (FIG. 16).

In an implanted state, after the clip 200 is in its locked position, thepump 250 and the cannula 150 are in a position suitable for long-termstability relative to the cuff 120 and the heart. While the clip 200 isin its locked position, an extremely large force is required to removethe cuff 120 from the cannula 150. For example, the force required toforcibly separate the pump 250 or cannula 150 from the cuff 120 whilethe clip 200 is in its locked position can be as large as the forcerequired to tear the cuff 120 from the heart.

The distance that the cannula 150 extends into a heart can be selectedin a similar manner as described above. For example, a cannula 150 witha proximal portion 152 having a particular length can be selected, oneor more spacers can be placed between the fastening member 122 and aheart, or the thickness of the fastening member 122 can be selected fora particular patient.

Referring to FIGS. 17A and 17B, an alternate implementation includes acuff 320 and a cannula 350 configured to cooperate with the pump 250 andthe clip 200. The cuff 320 defines an opening 330 that admits a proximalportion 352 of the cannula 350. A coupling mechanism in the form of anattachment member 326 engages a sealing ring 502 (FIG. 19A), such as ano-ring, disposed about the cannula 350 to couple the cuff 320 to thecannula 350. The clip 200 (FIG. 13A) acts as a locking mechanism toimpede the cuff 320 from becoming uncoupled from the cannula 350.

The cuff 320 includes an annular fastening member 322 that a cliniciancan fasten to heart tissue. For example, the fastening member 322 can beformed of a fabric such as PTFE felt. The cuff 320 includes a linkingmember 324 coupled to the fastening member 322, for example, by suturesor direct molding. The linking member 324 is formed of, for example, anelastomer such as silicone. The linking member 324 includes areinforcement member 325 (FIG. 18B), such as a mesh ring. The linkingmember 324 couples the attachment member 326 to the fastening member322, as described below.

The linking member 324 includes a bottom surface 328 that engages acircumferential flange 362 of the cannula 350. The primary sealingmechanism between the cuff 320 and the cannula 350 is the sealing ring502, and as a result, the linking member 324 and the circumferentialflange 362 are not required to form a seal. Nevertheless, in someimplementations, the linking member 324 may form a secondary seal withthe circumferential flange 362. In some implementations, the bottomsurface 328 engages a surface of the pump 250 as an alternative to, orin addition to, engaging a portion of the cannula 350.

The cannula 350 includes the proximal portion 352, the circumferentialflange 362, and a distal portion 354 housed within the pump 250. Thecannula 350 includes a circumferential taper 356 that engages acircumferential taper 405 of the attachment member 326, guiding the cuff320 into alignment with the cannula 350. The cannula 350 defines acircumferential groove 360 between a first circumferential ridge 358 anda second circumferential ridge 359. The circumferential groove 360receives the sealing ring 502.

Referring to FIGS. 18A and 18B, the attachment member 326 is formed of,for example, a rigid material such as metal or PEEK. The attachmentmember 326 includes a cylindrical portion 402, which defines an innercircumferential groove 404 that admits a portion of the sealing ring502. The sealing ring 502 is formed of, for example, an elastomer suchas silicone or implantable-grade ethylene propylene diene monomer(EPDM). In some implementations, the attachment member 326 does notdefine an inner circumferential groove 404 and instead has asubstantially cylindrical inner surface.

The attachment member 326 includes a flanged portion 406, for example, acircumferential flange that extends in a plane generally perpendicularto an outer wall 403 of the cylindrical portion 402. The attachmentmember 326 includes the inner circumferential taper 405 that engages thesealing ring 502, compressing the sealing ring 502 and permitting thesealing ring 502 to enter the inner circumferential groove 404.

The linking member 324 is molded over the attachment member 326, and theflanged portion 406 and the cylindrical portion 402 define holes 407that admit material of the linking member 324. The material of thelinking member 324 that extends through the holes 407 forms mechanicallocks that couple the linking member 324 to the attachment member 326.The linking member 324 is molded over an inner circumferential wall 408and an outer circumferential surface 410 of the cylindrical portion 402,as well as a top surface 412, a bottom surface 414, and acircumferential side surface 416 of the flanged portion 406.

Referring to FIGS. 19A and 19B, the sealing ring 502 is disposed in thecircumferential groove 360. To couple the cannula 350 to the cuff 320,the clinician moves the proximal portion 352 through the opening 330 ofthe cuff 320. The sealing ring 502 engages the circumferential taper 405of the attachment member 326, compressing the sealing ring 502 into thecircumferential groove 360.

As the cannula 350 advances through the opening 330, the sealing ring502 advances past the circumferential taper 405 to the position of FIG.19B. The sealing ring 502 expands into the circumferential groove 404 ofthe attachment member 326 and the bottom surface 328 of the linkingmember 324 engages the circumferential flange 362. The sealing ring 502is partially disposed in the circumferential groove 404 and partiallydisposed in the circumferential groove 360 of the cannula 350. Theengagement of the sealing ring 502 between the cuff 320 and the cannula350 limits travel of the cannula 350 relative to the cuff 320, couplingthe cannula 350 to the cuff 320. The expansion of the sealing ring 502into the circumferential groove 404 provides snap-like tactile feedbackto the clinician, indicating that the cannula 350 is coupled to the cuff320. The sealing ring 502 also creates a hemostatic seal between thecannula 350 and the cuff 320.

From the position of FIG. 19B, the clinician can move the clip 200 intoa locked position about the cuff 320 as described above with referenceto FIGS. 14A to 14C. With the clip 200 in its locked position (FIG. 20),the flanged portion 406 is captured between the clip 200 and thecircumferential flange 362, impeding the cuff 320 from becomingseparated from the cannula 350.

The distance that the cannula 350 extends into a heart can be selectedin a similar manner as described above. For example, a cannula 350 witha proximal portion 352 having a particular length can be selected, oneor more spacers can be placed between the fastening member 322 and aheart, or the thickness of the fastening member 322 can be selected fora particular patient.

Referring to FIG. 21, an alternate implementation include a cuff 620that couples to a cannula 650 of a pump 750. The cuff 620 defines anopening 630 that admits a proximal portion 652 of the cannula 650. Acoupling mechanism in the form of an attachment member 626 engages asealing ring 802 (FIG. 23B), for example, an o-ring disposed about thecannula 650, to couple the cuff 620 to the cannula 650. A clip 700 (FIG.25A) acts as a locking mechanism to impede the cuff 620 from becominguncoupled from the cannula 650.

Like the implementations described above, the cuff 620 can be coupled tothe pump 750 with a low profile, for example, in a distance from a heartthat is approximately the height of the cuff 620 along the cannula 650.The cuff 620 is coupled to the pump 750 by moving the cannula 650axially through the cuff 620. The locking mechanism, for example, theclip 700, can then be engaged to secure the position of the cuff 620about the cannula 650. Similar to the cam 28 and the clip 200, the clip700 moves into a locked position by moving in a plane perpendicular to acannula, which facilitates attachment of the cuff 620 to the pump 750 inthe low profile.

Referring to FIGS. 22A and 22B, the cuff 620 includes an annularfastening member 622 that a clinician can fasten to heart tissue. Forexample, the fastening member 622 can be formed of a fabric such as PTFEfelt. The cuff 620 includes a linking member 624 coupled to thefastening member 622, for example, by sutures or direct molding. Thelinking member 624 is formed of, for example, an elastomer such assilicone. The linking member 624 includes a reinforcement member 625(FIG. 22D), such as a mesh ring. The linking member 624 couples theattachment member 626 to the fastening member 622, as described below.

The linking member 624 includes a bottom surface 628 that engages acircumferential flange 662 (FIG. 23B) of the cannula 650. The primarysealing mechanism between the cuff 620 and the cannula 650 is thesealing ring 802, and as a result, the linking member 624 need not forma seal about the cannula 650. Nevertheless, in some implementations, thelinking member 624 may form a secondary seal through engagement with thecircumferential flange 662. In some implementations, the bottom surface628 engages a surface of the pump 750 as an alternative to, or inaddition to, engaging a portion of the cannula 650.

The linking member 624 defines a circumferential groove 632 in the outerdiameter of the cuff 620, located between the fastening member 622 and aflanged portion 634 of the linking member 624. The circumferentialgroove 632 receives a portion of the clip 700 to secure the cuff 620 tothe pump 750, as described further below. The linking member 624includes ridges 636 in the circumferential groove 632, for example,disposed on the flanged portion 634. The ridges 636 are spaced apart andextend approximately halfway along the height, H₂, of thecircumferential groove 632. When the clip 700 is in a locked positionabout the cuff 620, the clip 700 engages the ridges 636 to limitrotation of the cuff 620 about the cannula 650.

Referring to FIG. 22C, the attachment member 626 is formed of, forexample, a rigid material such as metal or PEEK. The attachment member626 includes a cylindrical portion 640 that has an outer wall 644 and aninner surface 642 that engages the sealing ring 802. The attachmentmember 626 includes a flanged portion 646, for example, acircumferential flange that extends in a plane generally perpendicularto the outer wall 644.

Referring to FIG. 22D, the linking member 624 is molded over theattachment member 626. The flanged portion 646 and the cylindricalportion 640 define holes 647 that admit material of the linking member624. The material of the linking member 624 that extends through theholes 647 forms mechanical locks that couple the linking member 624 tothe attachment member 626. The linking member 624 is molded over aninner circumferential wall 648, which can have a larger inner diameterthan the rest of the cylindrical portion 640. The linking member 624 isalso molded over an outer circumferential surface 610 of the cylindricalportion 640, as well as a top surface 612, a bottom surface 614, and acircumferential side surface 616 of the flanged portion 646. The innersurface 642 of the attachment member 626 remains exposed.

Referring to FIGS. 23A and 23B, the cannula 650 includes the proximalportion 652, the circumferential flange 662, and a distal portion 654housed within the pump 750. The cannula 650 includes a circumferentialtaper 656 that engages the attachment member 626, guiding the cuff 620into alignment with the cannula 650. The cannula 650 defines acircumferential groove 660 between a first circumferential ridge 658 anda second circumferential ridge 659. The sealing ring 802 is disposed inthe circumferential groove 660 and is formed of, for example, anelastomer such as silicone or implantable-grade EPDM.

To couple the cannula 650 to the cuff 620, the clinician moves theproximal portion 652 through the opening 630 of the cuff 620 (FIG. 23A).As the cannula 650 advances further, the sealing ring 802 engages theinner surface 642 of the attachment member 626, compressing the sealingring 802 into the circumferential groove 660 (FIG. 23B). The engagementof the sealing ring 802 with the inner surface 642 and the engagement ofthe bottom surface 628 with the circumferential flange 662 providetactile feedback to the clinician that the appropriate position has beenachieved.

The engagement of the sealing ring 802 between the cuff 620 and thecannula 650 limits travel of the cannula 650 relative to the cuff 620,coupling the cannula 650 to the cuff 620. The compression of the sealingring 802 between the cuff 620 and the cannula 650 also creates ahemostatic seal between the cannula 650 and the cuff 620. From theposition shown in FIG. 23B, the clinician can move the clip 700 into alocked position about the cuff 620 to secure the cuff 620 about thecannula 650, as described further below.

Referring to FIG. 24A, the sealing ring 802 has a cross-section 810 thatis substantially trapezoidal. The force required to insert the cannula650 into the cuff 620 using the sealing ring 802 is typically smallerthan the force required to insert the cannula 650 using a sealing ringthat has a round cross-section and a similar cross-sectional width. Insome instances, a lower insertion force is desirable to facilitateinstallation of the cannula 650 relative to the implanted cuff 620.

The cross-section 810 has an inner side 811, and outer side 812, a topside 813, and a bottom side 814. Adjacent sides 811, 812, 813, 814 areconnected by rounded corners 815. The inner side 811 faces toward thecannula 650 and is substantially flat. As a result, the inner surface ofthe sealing ring 810 is substantially cylindrical. The top side 813faces away from the pump 750, and the bottom side 814 faces toward thepump 750. The top side 813 and the bottom side 814 are substantiallyparallel to each other, for example, both sides 813, 814 aresubstantially perpendicular to the inner side 811.

The top side 813 and the bottom side 814 have different lengths. Thelength, L₁, of the top side 813 can be, for example, between one-fourthand three-fourths of the length, L₂, of the bottom side 814. Forexample, the length, L₁, of the top side 813 can be approximately halfor approximately two-thirds of the length, L₂, of the bottom side 814.The outer side 812 is angled, for example, forming substantiallystraight angled edge.

Referring to FIG. 24B an alternative sealing ring has a cross-section860. The cross-section 860 includes an upper portion 862 and a lowerportion 864, connected by a narrow neck 866. The sealing ring 850 thusincludes two stacked discs, connected by an annular band. Thecross-section 860 includes outer sides 870 engage the inner surface 642of the cuff 620, and inner sides 872 that engage the cannula 650 in thecircumferential groove 660.

Referring to FIGS. 25A and 25B, the clip 700 cooperates with features ofthe pump 750, described below, to limit movement of the cuff 620 (notshown) relative to the cannula 650. The clip 700 has an unlockedposition, in which the cuff 620 can be coupled about the cannula 650.The clip 700 also has a locked position, in which the clip 700 securesthe cuff 620 relative to the cannula 650. A component, such as a motorhousing 753 or an element attached to the motor housing 753, provides anupper surface 752 that defines channels 754. The clip 700 includes arms714 that extend into the channels 754 and travel along the channels 754as the clip 700 moves into its locked position.

The pump 750 captures the clip 700 between the upper surface 752 and acover 770. The cover 770 is attached over the upper surface 752 by, forexample, screws 772 or welds. The upper surface 752 and the cover 770define a slot 740 for the clip 700 to travel within. The slot 740permits the clip 700 to travel in a plane, for example, to travel in alinear direction, A, in a plane perpendicular to a longitudinal axis, Y,of the cannula 650.

Referring to FIGS. 26A-26C, the clip 700 includes a top side 702 thatfaces the cover 770, a bottom side 704 that faces the upper surface 752,and opposite lateral sides 706, 708. The clip 700 can be formed of, forexample, metal, such as titanium, or a rigid plastic, such as PEEK. Theclip 700 includes guide rails 712 and defines a recess or opening 715.The guide rails 712 stabilize the clip 700 laterally and guide the clip700 through a linear motion in the slot 740. The opening 715 admits atool or a finger of the clinician to facilitate retraction of the clip700.

The arms 714 of the clip 700 are curved and define an opening 720. Thearms 714 are resilient and can deflect laterally to capture the cuff620. Each arm 714 includes a post 719 that extends from the bottom side704 of the clip 700. Each post 719 is received in one of the channels754 (FIG. 25B) defined in the upper surface 752. The posts 719 aresubstantially cylindrical and extend perpendicular to, for example, aplane defined along the top side 702 of the clip 700. When the clip 700is located in the slot 740, the posts 719 extend substantially parallelto the longitudinal axis, Y, of the cannula 650. As the clip 700 movesrelative to the pump 750, the posts 719 travel through the channels 754.

In the locked position of the clip 700, the arms 714 extend about thecuff 620 and extend into the circumferential groove 632. The arms 714have a substantially smooth inner surface 722 that engages the linkingmember 624 in the circumferential groove 632. The arms 714 also includeteeth 716 (FIG. 26B) that fit between the ridges 636 to limit rotationof the cuff 620 relative to the clip 700. The teeth 716 can be disposedon the arms 714 and on a central extension 724 of the clip 700. Threeteeth 716 are shown, positioned to press radially inward on the cuff 620when the clip 700 is in its locked position. More teeth or fewer thanthree teeth can be used to promote rotational stability of the cuff 620.

The teeth 716 have an angled or chamfered edge 726 (FIG. 26D),permitting the teeth 716 to engage the cuff 620 when the cuff 620 is notfully seated against the circumferential flange 662. As the clip 700moves into its locked position, the teeth 716 move radially inwardtoward the circumferential groove 632. The chamfered edge 726 engagesthe flanged portion 634 of the cuff 620, forcing the cuff 620 toward theupper surface 752 into a fully seated position against thecircumferential groove 662.

The clip 700 includes substantially flat end portions 730 that arecaptured between the upper surface 752 and the cover 770. The cover 770impedes the end portions 730 from moving away from the surface 752, andthus holds the posts 719 in the channels 754. Engagement of the endportions 730 between the upper surface 752 and the cover 770 also limitstwisting along the arms 714 in response to axial loads exerted along thearms 714. The end portions 730, the teeth 716, and stabilizing posts 732on the arms 714 can each have a height, H₂, along the longitudinal axis,Y, that is substantially the same as a corresponding height of the slot740, thereby limiting travel of the clip 700 along the longitudinal axisand limiting tilting of the clip 700 within the slot 740.

The clip 700 includes a latch 733 that engages the cover 770 to limitretraction of the clip 700 from the locked position. The latch 733includes a deflection beam 737 and an extension 738 located on a freeend 739 of the deflection beam 737. The extension 738 extends from thetop side 702 of the clip 700. The deflection beam 737 provides aresilient force that holds the extension 738 in a mating receptacle of,for example, the cover 770, unless overcome by a sufficient force.

The clip 700 includes ramp features 735 that extend from the bottom side704. The ramp features 735 wedge the clip 700 between the cover 770 andthe upper surface 752, stabilizing the clip 700 along the longitudinalaxis, Y, of the cannula 650 when the clip 700 is in the locked position.By forcing the top side 702 toward the cover 770, the ramp features 735also force engagement of the latch 733 to the mating receptacle.

The clip 700 includes visual indicators 736 on the bottom side 704 thatindicate when the clip 700 is out of the locked position. The visualindicators 736 are, for example, recesses containing a colored materialthat is easily noticeable by a clinician. The visual indicators 736 areexposed, and thus visible from the bottom of the pump 750, when the clip700 is not in the locked position. The visual indicators 736 areobscured when the clip 700 is in the locked position.

Referring to FIG. 27, the channels 754 in the surface 752 direct travelof the arms 714 as the clip 700 moves in the slot 740. As the clip 700moves between an unlocked position to the locked position, the posts 719move through the channels 754. The channels 754 have a width, W₂, thatis larger than a diameter of the posts 719, which permits differentlateral positions of the posts 719 in the channels 754. As describedfurther below, the width, W₂, permits the posts 719 travel alongdifferent paths in the channels 754, rather than being constrained totravel along a single path.

The channels 754 are defined by inner walls 760 and outer walls 762. Alateral distance, D, between the inner walls 760 is greater than adistance between the posts 719 when the arms 714 are not flexed. As aresult, positioning the posts 719 in the channels 754 flexes the arms714 away from each other, causing the arms 714 to exert a resilientinward force against the inner walls 760. As the clip 700 travels in theslot 740, the posts 719 slide along the inner walls 760 unless displacedby, for example, the cuff 620.

The channels 754 define features that receive the posts 719. Eachchannel 754 defines, for example, a first end 764, a second end 765, anda detent 766, each of which can receive one of the posts 719. The posts719 reside in the first ends 764 in an unlocked position of the clip700, for example, when the clip 700 is fully retracted. At the firstends 764, the posts 719 engage the walls to impede the clip 700 fromseparating from the pump 750 by sliding out of the slot 740 along arrowA. The posts 719 reside in the second ends 765 when the clip 700 is inthe locked position. The posts 719 reside in the detents 766 when theclip 700 is in a restrained position, for example, in which engagementof the posts 719 in the detents 766 impedes the clip 700 from travellingfurther toward the locked position. The unlocked position, the lockedposition, and the restrained position are stable positions of the clip700 within the slot 740.

Referring to FIG. 28A, the clip 700 is retracted in the direction ofarrow B₁, and each post 719 travels along a path 767 between the secondend 765 and the first end 764. Various positions of the posts 719 areshown, but other features of the clip 700 are not shown. The pump 750can be provided to a clinician with the clip 700 in the locked position,with the posts 719 residing in the second ends 765. In someimplementations, the arms 714 are in a relaxed state in the lockedposition. The clinician retracts the clip 700 to permit the cannula 650to be coupled to the cuff 620.

Referring to FIG. 28B, when the cuff 620 is not coupled about thecannula 650, advancing the clip 700 from the unlocked position towardthe locked position places the clip 700 in the restrained position. Asthe clip 700 advances in the direction of arrow B₂, the arms 714 exert alateral force inward toward the cannula 650, causing the posts 719 totravel in a path 768 along the inner walls 760. The posts 719 enter thedetents 766 to impede the clip 700 from entering the locked position.

The clip 700 enters the restrained position when the cuff 620 is notproperly coupled to the cannula 650, for example, when the cuff 620 isnot located about the cannula 650 or the cuff 620 is improperly placedabout the cannula 650. The placement of the clip 700 in the restraineddiscourages premature locking of the clip 700 and indicates to theclinician that the cuff 620 is not properly placed about the cannula650. Patient safety is enhanced because the clip 700 does not enter thelocked position if doing so would not actually secure the cuff 620 tothe pump 750.

In some implementations, the clip 700 can enter the restrained positionwhen only one of the posts 719 engages one of the detents 766. Eitherpost 719 can independently impede the clip 700 from entering the lockedposition. In some instances, the cuff 620 may be seated only partiallyagainst the circumferential flange 662. For example, the cuff 620 may beplaced in a tilted orientation such that the cuff 620 is not aligned ina plane perpendicular to the cannula 650. With the cuff 620 partiallyseated, one of the posts 719 may avoid the detent 766. Engagement of theother post 719 with its corresponding detent 766, however, will placethe clip 700 in the restrained position rather than permitting the clip700 to enter the locked position.

Referring to FIG. 28C, when the cuff 620 is properly coupled to thecannula 650, advancing the clip 700 in the direction of arrow B₂ movesthe clip 700 into the locked position about the cuff 620. For clarity inillustration, the fastening member 622 and portions of the linkingmember 624 are not shown.

When the cuff 620 is coupled to the cannula 650, the flanged portions634, 646 of the cuff 620 cover the detents 766. The cuff 620 blocks theposts 719 from entering the detents 766 and permits the posts 719 toenter the second ends 765. Between the unlocked position and the lockedposition, the posts 719 move along a path 769. The posts 719 slide alongthe outer circumference of the flanged portion 646, engaged to the cuff620 by the resilient force of the arms 714, until the posts 719 reachthe second ends 765. In the locked position, the arms 714 (not shown)extend into the circumferential groove 632, capturing the flangedportions 634, 646 between the arms 714 and the circumferential flange662 of the cannula 650. The teeth 716 extend radially inward into thecircumferential groove 632, becoming enmeshed between the ridges 636 tolimit rotation of the cuff 620 relative to the cannula 650.

Referring to FIGS. 29A and 29B, when a clinician installs the pump 750,the visual indicators 736 on the clip 700 are exposed to the clinician'sview. The visual indicators 736 indicate that the clip 700 is notsecuring the cuff 620, and thus that installation is incomplete. Thevisual indicators 736 are exposed in the unlocked position (FIG. 29A)and in the restrained position (FIG. 29B).

Referring to FIG. 29C, when the clip 700 enters the locked position, thepump 750 obscures the visual indicators 736, indicating to the clinicianthat the clip 700 has been properly locked about the cuff 620.

Referring to FIGS. 30A-30C, the cover 770 defines a mating receptacle774, for example, a recess or an opening, that cooperates with the latch733. The latch 733 does not secure the position of the clip 700 in theunlocked position (FIG. 30A) or the restrained position (FIG. 30B). Inthe locked position (FIG. 30C), the extension 738 extends into themating receptacle 774 to impede retraction of the clip 700 in thedirection of the arrow R.

Referring to FIG. 31, the extension 738 includes an angled leading edge742 and an angled trailing edge 744 that engage the cover 770. Theleading edge 742 engages an outer edge 746 of the cover 770 as the clip700 travels into the locked position. The engagement of the leading edge742 with the outer edge 746 deflects the deflection beam 737, permittingthe extension 738 to slide under the outer edge 746 and into the matingreceptacle 774. The trailing edge 744 engages an inner surface 748 ofthe mating receptacle 774 to limit removal of the clip 700.

The trailing edge 742 has a steeper slope than the leading edge 742. Forexample, the trailing edge 742 can have a slope of between approximately70 degrees and approximately 85 degrees, and the leading edge can have aslope of between approximately 10 degrees to approximately 60 degrees.As a result, the amount of force required to dislodge the extension 738from the mating receptacle 774 is greater than the force required toinsert the extension into the mating receptacle 774. When removal of theclip 700 is desired, a clinician can engage a tool with the deflectionbeam 737 to move the extension 738 out of the mating receptacle 774,which permits the clip 700 to be retracted.

In some implementations, a plug can be fabricated for a cuff 20, 120,320, 620. A plug can be placed in the opening 30, 130, 330, 630 of animplanted cuff 20, 120, 320, 620 after a pump 12, 250, 750 has beenexplanted. The plug can fill the opening 30, 130, 330, 630 to preventblood from escaping through the cuff 20, 120, 320, 620 after the pump12, 250, 750 is removed. Plugs can include features similar to thosedescribed for the cannulas 50, 150, 350, 650. As a result, a plug can becoupled to a corresponding cuff 20, 120, 320, 620 using one or more ofthe same mechanisms that couple a cuff 20, 120, 320, 620 to a cannula50, 150, 350, 650. A plug can be further secured to a heart or to a cuff20, 120, 320, 620 by sutures.

A number of implementations have been described. Nevertheless, it willbe understood that various modifications may be made without departingfrom the spirit and scope of the disclosure. Implementations can includeany appropriate combination or subcombination of features describedabove. For example, some of or all of the features described for thepumps 50, 250, 750, cuffs 20, 120, 320, 620, cannulas 50, 150, 350, 650,and clips 200, 700 can be combined or implemented individually.Accordingly, other implementations are within the scope of the followingclaims.

What is claimed is:
 1. A cuff for attachment to a heart, comprising: amember defining an opening; a linking member coupled to the member anddisposed about the opening; and an attachment member coupled to thelinking member and disposed about the opening, the linking memberextending about an outer surface of the attachment member, theattachment member configured to attach the cuff to a cannula disposedthrough the opening, the attachment member having at least one flangedportion extending outward from the opening in a plane generallyperpendicular to a circular portion of the attachment member.
 2. Thecuff of claim 1, wherein the linking member is molded over a portion ofthe attachment member, and the attachment member is coupled to themember through the linking member.
 3. The cuff of claim 1, wherein theattachment member comprises at least one extension disposed generallyperpendicular to the member, the extension having a tapered portiondisposed on a surface of the extension facing toward the opening.
 4. Acuff for attachment to a heart, comprising: a member defining anopening; a seal coupled to the member and disposed about the opening;and a clamp coupled to the seal and disposed about the opening, theclamp having a first end and a second end, the clamp configured suchthat (i) bringing the first end near the second end opens the clamp and(ii) moving the first end and the second end apart closes the clamp.